JPS6229000B2 - - Google Patents

Description

[Detailed description of the invention]

Normally, in plastic working of metals, when the workpiece is heated above the recrystallization temperature, it is called hot working, and when it is heated below the recrystallization temperature, it is called warm working, and when the workpiece is worked at room temperature. When this is done, it is called cold working. The recrystallization temperature of metal materials varies depending on the material, and is 600 to 700°C for steel, about 300°C for copper, and about 200°C for aluminum. For steel materials, which are most in demand among metal materials, the heating temperature during hot working is 1100 to 1250°C; for example, for stainless steel, the heating temperature during warm working is
250℃ due to decrease in ductility due to precipitation at around 400℃.
-350℃ or 500-700℃ is selected. The present invention relates to a lubricant for performing plastic working such as forging and deep drawing or powder forming at 250 to 350°C. Therefore, as long as it is processed in the temperature range of 250 to 350℃, it is not limited to steel materials, but also other general structural materials. 250
It may be a functional material such as a material that exhibits a superplastic phenomenon at around ℃. Further, it does not matter whether this temperature range corresponds to hot working or warm working of the material to be processed. By the way, as mentioned above, in warm forging of stainless steel and warm drawing of stainless steel plates, the process is performed after heating to 250 to 350°C. However, there is no suitable lubricant for this temperature range, and the development of a lubricant is currently awaited. In other words, for cold forging of steel, it is a lubricant that combines a phosphate film and metal soap (zinc stearate), and is well known as Bonderite and Bondarium. However, in this case, it is generally not possible to use Bonderite Bondaryube at temperatures between 250 and 350°C, since metal soaps decompose at about 200°C. Furthermore, in the case of Bonderite and Bondaryube, the process for strongly adhering the phosphate film to the surface of the processed material is complicated, and care must be taken to dispose of the waste liquid to prevent pollution. There are high hopes for a lubricant that can be used easily. In addition to Bonderite and Bondaryube, there are other lubricants for cold plastic working such as animal and vegetable oils, mineral oils, and synthetic oils, which are used in rolling, drawing, deep drawing, etc. However, the operating temperature of these lubricants is limited to 200°C, and even when extreme pressure additives such as phosphorus, chlorine, and sulfur are added and mixed, the operating temperature is limited to 250°C or lower. . On the other hand, graphite-based lubricants and glass lubricants are well known as lubricants for hot forging, but these are suitable for use at temperatures above 500℃, and their lubrication performance is limited between 250 and 350℃. I can't expect much. In view of this situation regarding lubricants, the present inventors
As a result of intensive research to develop a lubricant for plastic processing at temperatures between 250 and 350℃, we found that by adding and mixing tetrafluoroethylene resin powder to a heat-resistant resin powder base, we achieved heat resistance and lubrication. We have developed a new lubricant that has both properties. That is, polyimide and polyamideimide are known as heat-resistant resins, and polyimide in particular has a heat resistance of about 350°C, while polycarbonate,
This is significantly superior to conventional plastics such as nylon, polystyrene, and epoxy resin, which have a heat resistance temperature of only 200℃ or less. The present invention applies the heat resistance of polyimide to a lubricant for plastic working at 250 to 350°C, and uses a powdered lubricant. However, the sliding properties of polyimide are not necessarily good, so in order to improve the sliding properties, polytetrafluoroethylene resin powder, which is a fluororesin type, is added and mixed. Here, tetrafluoroethylene resin is well known as a material with a small coefficient of friction in cold conditions, but it is very expensive and its heat resistance is limited to 260°C. Therefore, by adding and mixing tetrafluoroethylene resin powder to a heat-resistant resin polyimide as a main component, we aim to improve the heat resistance of tetrafluoroethylene resin and reduce the amount of tetrafluoroethylene resin used. The objective is to develop an economically advantageous lubricant. Furthermore, in order to increase the adhesion and adhesion of these mixtures to workpiece materials and molds, and to reduce the amount of tetrafluoroethylene resin used, varnish-like methylphenyl silicone resin is added and mixed. Note that an N-methyl-2-pyrrolidone solution is used as a solvent for the mixture of polyimide resin powder, tetrafluoroethylene resin powder, and methylphenyl silicone resin. The weight distribution ratio of polyimide powder (represented by P), tetrafluoroethylene resin powder (T), methylphenyl silicone resin (M), and N methyl-2 pyrrolidone solution (N) is P:T:M:N= 1:(0.25~2.0):1:5
These are mixed and stirred according to formula (1). This is used as a lubricant and applied to the test piece and tool, which are the materials to be machined. Next, the lubricant is dried by heating at 230°C for 30 minutes. Then, by the ring compression test method as shown in Figure 1 of the attached drawings.
When we calculated the friction coefficient μ at 250 to 350℃, we obtained the formula (1)
When the amount of tetrafluoroethylene resin powder (T) added was 0.25 to 2.0, the friction coefficient μ was 0.03 to 0.05, and the lubrication performance was extremely good. in this case,
The standard heating time for the lubricant at a given temperature was 15 minutes, but it is desirable that this heating time be shorter. The amount of ethylene tetrafluoride resin powder (T) added is determined by the formula
If it is less than 0.25 to 2.0 shown in (1), the lubricating effect of the tetrafluoroethylene resin will not be sufficiently exhibited and the lubricating effect will be poor. On the other hand, if the amount added is larger than this, the relative cost will be high because tetrafluoroethylene resin is expensive, and T will be
Since the friction coefficient becomes almost constant between 0.25 and 2.0, this addition amount is sufficient. In this way, the amount of the tetrafluoroethylene resin powder added is from 0.25 to 0.25, as shown in formula (1).
2.0 is appropriate. Although powdered heat-resistant resin polyimide was used, it is of course possible to use varnish-like heat-resistant resin polyimide instead of powder. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 The weight blending ratio of polyimide powder (P), tetrafluoroethylene resin powder (T), methylphenyl silicone resin (M), and N methyl-2-pyrrolidone solution (N) was P:T:M:N = 1:
Experiments were conducted for the cases of 0.50, 1.0, and 2.0, and the results are shown in Figure 2. By setting the amount X of the tetrafluoroethylene resin in the range of 0.25 to 2.0 in this manner, the friction coefficient μ is considerably reduced compared to the case where X=0, and the resin exhibits performance as a lubricant. The test conditions are as follows. [Test conditions] Test method: Ring compression test The ring compression test is a method in which a ring-shaped test piece 1 is pressurized and plastically deformed between flat tools (pressure plates) shown at 3 in Figure 1a of the attached drawings. , The test piece, which is the workpiece material, can be determined from the degree of expansion of the inner and outer diameters of the test piece (see Figure 1b, the solid line shows the state before the test, and the broken line shows the deformed state after the test). This method calculates the friction coefficient μ between the tool and the tool (the surface indicated by 2 in FIG. 1a). Same compression ratio (△
H/Ho=(Ho−H)/Ho) When the lubrication condition is better, that is, when the friction coefficient is smaller, the inner diameter becomes larger. Rate of change of this inner diameter Ri/ri
The relationship between (Ri: inner radius after deformation, ri: initial inner radius) and compression ratio △H/Ho is expressed by Kunoki's formula (Science Research Institute Report, Vol. 30, No. 2, March 1952). ), it can be found by calculation using the friction coefficient μ as a parameter. Therefore, by experimentally measuring Ri/ri and ΔH/Ho, it is possible to know the friction coefficient μ of the lubricant in that case. Test temperature: The test piece and tool were heated to 300℃ for approximately 15 minutes, and then forged using a crank press (processing speed approximately 6.3 m/min). Test piece (workpiece material) material: Zn-22Al superplastic material. The specimens are polished with 1000 emery paper and degreased with acetone before applying the lubricant. Dimensions of test piece: Inner diameter x Outer diameter x Height = 2ri x 2ro x Ho
=12.51〓×25.07〓×6.24=2:4:1 Method of applying lubricant: After applying it to both the test piece and tool, dry it at 230℃ for 30 minutes. Tool: The material is SKD61, and the surface roughness of the surface in contact with the test piece is 0.3 μm. Before applying lubricant to the surface of the tool, sand it with 1000-grit emery paper and then degrease it with acetone. Example 2 According to the experiment at 300°C in Example 1, the amount X of tetrafluoroethylene resin added in formula (2) was 0.25 to 2.0.
was found to be appropriate. Therefore, the amount of X added is within this range, that is, X = 0.25, 0.50, 1.0,
For case 2.0, experiments were conducted at test temperatures other than 300°C, and the results are shown in Table 1, including the results at 300°C. In Table 1, the test temperature is 250
In the range of ~350°C, the friction coefficient μ is 0.03 to 0.05, and the lubrication performance is extremely good. However, since the lubricant of the present invention has a friction coefficient μ of 0.09 to 0.12 in cold conditions (test temperature 20° C.), it is not suitable as a lubricant for cold plastic working. However, since the friction coefficient μ at 200℃ is about 0.055,
It exhibits sufficient lubrication performance not only in the temperature range of 250 to 350°C, but also in the temperature range of 200 to 350°C. [Test conditions] All conditions were the same as in Example 1 except for the test temperature.

〔Test conditions〕

This is the same as in Example 2.

【table】 [Brief explanation of the drawing]

Figure 1a shows the ring compression test method, where 1 is the ring compression test piece, 2 is the surface to which lubricant is applied where the test piece and the tool (pressure platen) are in contact, and 3 is the ring compression test method. 4 indicates a tool (pressure plate), and 4 indicates a press slide for applying pressure. On the other hand, the first
Figure b shows the change in shape of the ring compression test piece before and after deformation, where the solid line represents the state before deformation and the broken line represents the state after deformation. Figure 2 shows the amount of added tetrafluoroethylene resin X (formula
(2)).

Claims (1)

[Claims] 1. Polyimide (indicated by P), which is a heat-resistant resin;
Tetrafluoroethylene resin powder (indicated by T) was used as a lubricant, methylphenyl silicone resin (indicated by M) was used as an adhesive for the workpiece material and tool, and N methyl-2-pyrrolidone solution (indicated by N) was used as a solvent for these. A lubricant for plastic working which is prepared by blending (shown) in a weight mixing ratio of P:T:M:N=1:(0.25-2.0):1:5.